New Method for Assessment Ageing Condition of Oil Impregnated Insulation Pressboard Based on Frequency Domain Spectroscopy

2014 ◽  
Vol 513-517 ◽  
pp. 323-327 ◽  
Author(s):  
Jian Hao ◽  
Jin Fu ◽  
Pei Guo ◽  
Gao Lin Wu ◽  
Qian Wang ◽  
...  
Keyword(s):  
Dielectric Loss ◽  
Moisture Content ◽  
Frequency Domain ◽  
Condition Assessment ◽  
New Method ◽  
Time Saving ◽  
Interpolation Curve ◽  
Ageing Condition ◽  
Cellulose Insulation

It is important to assess the condition of the cellulose insulation in transformer. However, taking paper samples from a transformer is both impractical and destructive. In this paper, a new method for assessment ageing condition of oil impregnated insulation pressboard based on frequency domain spectroscopy (FDS) was proposed. The FDS measurements were taken on oil impregnated insulation pressboards with five ageing levels at moisture content of 1.22%, 2.06%, 3.02% and 3.87%. The dielectric loss of all the samples were calculated bytanδ (f)interpolationandthe ageing condition assessment database which contains data of five ageing levels and 1%-4% moisture content was built. It is found that thetanδ (f)interpolation is more sencentive to ageing and moisture. It could realize the ageing condition assessment by comparing thetanδ (f)interpolation curve with the curves in the database.The assessing result of the middle-low main insulation life of a 220kV transformer valided that it is effective and time saving to use the new method for ageing condition assessment.

scholarly journals A New Method for Evaluating Moisture Content and Aging Degree of Transformer Oil-Paper Insulation Based on Frequency Domain Spectroscopy

Energies ◽  
2017 ◽  
Vol 10 (8) ◽  
pp. 1195 ◽  
Author(s):  
Guoqiang Xia ◽  
Guangning Wu ◽  
Bo Gao ◽  
Haojie Yin ◽  
Feibao Yang
Keyword(s):  
Moisture Content ◽  
Frequency Domain ◽  
Transformer Oil ◽  
New Method ◽  
Paper Insulation

scholarly journals A Modified Aging Kinetics Model for Aging Condition Prediction of Transformer Polymer Insulation by Employing the Frequency Domain Spectroscopy

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2082 ◽  
Author(s):  
Jiefeng Liu ◽  
Xianhao Fan ◽  
Yiyi Zhang ◽  
Hanbo Zheng ◽  
Zixiao Wang ◽  
...  
Keyword(s):  
Moisture Content ◽  
Frequency Domain ◽  
Degree Of Polymerization ◽  
Kinetics Model ◽  
Model Parameters ◽  
Aging Condition ◽  
Feature Parameter ◽  
Aging Kinetics ◽  
Cellulose Insulation ◽  
Potential Tool

The aging kinetics model is of great interest to scholars since it is capable of describing the variation law between the degree of polymerization (DP) and the aging duration of transformer polymer (cellulose) insulation. However, it is difficult to determine the moisture content inside the transformer polymer insulation without destroying it, so that the model parameters cannot be confirmed. Such limitation greatly restricts its application. It is interesting to note that as long as the moisture content of the transformer polymer insulation could be characterized (replaced) by a certain feature parameter, the above issue will be solved naturally. The existing researches indicate that the Frequency Domain Spectroscopy (FDS) is sensitive to moisture. Consequently, the feature parameter that could characterize the moisture inside transformer polymer insulation (extracted from the FDS curve) can be used to report a modified aging kinetics model, which could perform the aging condition prediction of transformer polymer insulation under various test conditions, including aging duration, aging temperature, and initial moisture. In that respect, the average relative error of prediction results of prepared samples is equal to 7.41%, which reveals that the reported model might be serviced as a potential tool for the aging condition prediction of transformer polymer insulation.

scholarly journals Effect of Radial Moisture Distribution on Frequency Domain Dielectric Response of Oil-Polymer Insulation Bushing

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1219 ◽  
Author(s):  
Daning Zhang ◽  
Guanwei Long ◽  
Yang Li ◽  
Haibao Mu ◽  
Guanjun Zhang
Keyword(s):  
Moisture Content ◽  
Space Charge ◽  
Frequency Domain ◽  
Water Distribution ◽  
Space Charge Polarization ◽  
Moisture Distribution ◽  
Mechanism Analysis ◽  
Loss Peak ◽  
Charge Polarization ◽  
Peak Value

In order to realize the diagnosis of water distribution, this paper analyzes the interface polarization and macroscopic space charge polarization mechanism when the water distribution is non-uniform. The experimental results of this paper and bushing show that when the moisture distribution is non-uniform, there is a significant loss peak in the tanδ-f curve. The loss peak shifts to higher frequencies as the non-uniformity coefficient increases. There are common intersection points between multiple tanδ-f curves. Further, this paper realizes the diagnosis of the location of moisture distribution through Frequency Domain Spectroscopy (FDS) testing of different voltages and different wiring methods based on the macroscopic space charge polarization. In the single-cycle FDS test, when the positive electrode is first added to the area with higher moisture content, the amplitude of the tanδ-f curve is smaller. The tanδ-f curves under different wiring methods constitute a “ring-shaped” loss peak. As the voltage increases, the peak value of the loss peak shifts to the lower frequency band. As the temperature increases, the peak value of the loss peak shifts to higher frequencies. Based on the above rules and mechanism analysis, this research provides a new solution for the evaluation of moisture content of oil-immersed polymers equipment.

Microwave Nondestructive Sensing of Moisture Content and Water Activity of Almonds

2021 ◽  
Vol 64 (4) ◽  
pp. 1373-1379
Author(s):  
Samir Trabelsi
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Bulk Density ◽  
Water Activity ◽  
Free Space ◽  
Loss Factor ◽  
Dielectric Loss Factor ◽  
List Type

HighlightsMoisture and water activity were determined nondestructively and in real time from measurement of dielectric properties.Moisture and water activity calibration equations were established in terms of the dielectric properties.Situations in which bulk density was known or unknown were considered.SEC ranged from 0.41% to 0.68% for moisture and from 0.02 to 0.04 for water activity.Abstract. A method for rapid and nondestructive determination of moisture content and water activity of granular and particulate materials was developed. The method relies on measurement of the dielectric constant and dielectric loss factor at a single microwave frequency. For the purpose of illustration, the method was applied to predicting the moisture content and water activity of almond kernels. A free-space transmission technique was used for accurate measurement of the dielectric properties. Samples of Bute Padre almond kernels with moisture content ranging from 4.8% to 16.5%, wet basis (w.b.), and water activity ranging from 0.50 to 0.93 were loaded into a Styrofoam sample holder and placed between two horn-lens antennas connected to a vector network analyzer. The dielectric properties were calculated from measurement of the attenuation and phase shift at 8 GHz and 25°C. The dielectric properties increased linearly with moisture content, while they showed an exponential increase with water activity. Situations in which the bulk density was known and unknown were considered. Linear and exponential growth regressions provided equations correlating the dielectric properties with moisture content and water activity with coefficients of determination (r2) higher than 0.96. Analytical expressions of moisture content and water activity in terms of the dielectric properties measured at 8 GHz and 25°C are provided. The standard error of calibration (SEC) was calculated for each calibration equation. Results show that moisture content can be predicted with SECs ranging from 0.41% to 0.68% (w.b.) and water activity with SECs ranging from 0.02 to 0.04 for almond kernel samples with water activity ranging from 0.5 to 0.9 and moisture contents ranging from 4.8% to 16.5% (w.b.). Keywords: Bulk density, Dielectric constant, Dielectric loss factor, Free-space measurements, Loss tangent, Microwave frequencies, Moisture content, Water activity.

Compressibility curves as a quantitative measure of soil tilth, II

1938 ◽  
Vol 28 (3) ◽  
pp. 367-378 ◽  
Author(s):  
G. W. Scott Blair ◽  
G. H. Cashen
Keyword(s):  
Moisture Content ◽  
Quantitative Measure ◽  
New Method ◽  
Complete Analysis

1. The method described in an earlier paper for measuring the compressibility of soils in situ has been used to study the gradual consolidation of soil following digging with a fork, and a new method in which the rate of flow of water through rubber tubes buried in the soil gives a measure of compression, is described.2. By means of this latter method some measure can be obtained of the changes that take place in the soil after it has been loaded and trampled.3. The results of the experiments confirm and amplify the earlier conclusions. Without further data it is hard to distinguish quantitatively the effects of moisture and time, but it is of interest that whereas the compressibility of newly dug soils is hardly affected by differences in moisture for the range of stress used, that of soils which have rested for some time since cultivation is much increased by an increase in moisture content.4. Experiments on a wider scale should be undertaken in order that a more complete analysis may be effected.

Effect of moisture content on dielectric properties of banana leaves and peels in frequency range of 1–20 GHz

Frequenz ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Soumya Sundar Pattanayak ◽  
Soumen Biswas
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Measurement Data ◽  
Banana Peel ◽  
Frequency Range ◽  
Proposed Model ◽  
Banana Leaves ◽  
Banana Leaf

Abstract The quality of agricultural products can be remotely sensed and enhanced by determining the dielectric properties. This paper studies the dielectric properties of banana leaf and banana peel over the frequency range 1–20 GHz using the open-ended coaxial probe (OCP) method. A new curve fitting model is proposed to characterize the dielectric properties of banana leaf and banana peel. The different moisture content (MC) levels are considered for both banana leaf and banana peel samples and, their dielectric properties are characterized. Further, the banana leaf and banana peel’s measurement data are compared with the data obtained using the proposed model. In addition, Root Mean Square Error (RMSE) and R-squared (R 2) are calculated to validate the performance of the proposed model. In case of banana leaf at 68.26% MC, the dielectric constant achieves the value of R 2 and RMSE of 0.98 and 0.0648, respectively. Similarly, dielectric loss achieves the value of R 2 and RMSE of 0.88 and 0.0795, respectively. Further, for banana peel at 80.89% MC, the dielectric constant achieves the value of R 2 and RMSE of 0.99 and 0.2989, respectively. Similarly, dielectric loss achieves the value of R 2 and RMSE of 0.96 and 0.6132, respectively.

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